<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
    <script src="myCommon.js"></script>
</head>
<body>
<input type="button" id="btn" value="点我">
<script>
 var btn = $('btn');
 function foo(){
     console.log('aa');
 }
foo();
foo();
foo();
foo();
foo();

</script>
</body>
</html>